As mentioned by [1]},
absorption could in general be due
to a disc wind.
This wind could be dusty, with the radiation pressure playing a key role and the dust porosity and size evolving significantly while being transported by the wind [2]}.
[3]} find that the mass-loss rate in the wind of PDS 70 is \(\dot{M} _{\mathrm {wind}}\sim 10^{-11}~{M_\odot }\,\mathrm {yr}^{-1}\sim 10^{-8}~M_{\mathrm {J}}\,\mathrm {yr}^{-1}\) , which might lead to a very small surface density given the large area over which it is spread.
However, estimating the absorption by a disc wind in detail is well beyond the scope of this work.
